1. Field of the Invention
The present invention relates to a motorized roller such as a motor pulley and a motor roller used in a conveyor or the like.
2. Description of the Related Art
Various motorized rollers have been conventionally proposed. Such a roller has a roller body and a motor contained in the roller body, and the motor rotates the roller body. This type of motorized roller is, as shown in FIG. 5 for example, used as a motor roller MR, which is disposed on a conveyor 2 to directly convey a package 4. Otherwise, the motorized roller, as shown in FIG. 6, may be used as a motor pulley MP for conveying a package 4 with the use of a belt 6.
FIG. 7 schematically shows a side sectional view of a conventionally known motorized roller 10 (refer to, for example, Japanese Patent Laid-Open Publication No. 1994-227630).
This motorized roller 10 comprises a roller body 11 of a substantially cylindrical member, a motor 12, and a reducer 13. The motor 12 and the reducer 13 are contained in the internal space of the roller body 11. Both ends of the roller body 11 are rotatably supported by a pair of first and second attachment brackets 14 and 15. The roller body 11 is rotatable in its peripheral direction. The motor 12 being an induction motor comprises a stator 16 which is composed of a coil wound around an iron core, and a cage-shaped rotor 17 coaxially disposed in the internal space of the stator 16.
In the motorized roller 10, when the motor 12 is energized, a motor shaft 12A rotates, and the reducer 13 slows down the rotation of the motor shaft 12A. Slowed output is transmitted to the roller body 11, so that the roller body 11 rotates in its peripheral direction.
By the way, when such a motorized roller 10 conveys a large package, it is necessary to increase the driving force of the motorized roller 10. Thus, a high power type of induction motor is adopted as the motor 12.
In the conventionally known motorized roller 10, however, heat generated from the motor 12 and the reducer 13 tends to accumulate in the roller body 11 due to its structure, so that there is a limit to reduction of temperature rise. Accordingly, taking a case of boosting the motor 12 at, for example, 0.1 kw or more to increase the driving force of the motorized roller 10, continuous operation time is restrained, and hence it seriously obstructs an operation schedule. In some cases, it is necessary to install a protective device to prevent the motor 12 from being burnt.
Due to restraint in motor power and/or the continuous operation time, for example, when conveying a large package with the motor roller MR, a plurality of motor rollers MR with low capacity are necessary to increase the whole driving force. Thus, there is a problem of increase in cost. To convey a large package by a single motor roller MR, it is necessary to enlarge the diameter of the motor. Thus, the external diameter of the roller is also enlarged, so that there is a problem that conveyor equipment such as a conveyor becomes large.